Bloomberg News, Jeffrey Burke

As New Orleans dug itself out of the mess left by Hurricane Katrina, Sheri Fink began digging into puzzling deaths at one of the city’s hospitals.

She won a Pulitzer Prize in 2010 for investigative reporting that has now grown into a book, “Five Days at Memorial: Life and Death in a Storm-Ravaged Hospital.” It’s a marvel of journalistic effort that brings an objective and sympathetic eye to the suffering and tough decisions at Memorial Medical Center.

What it’s not is an easy read. Densely detailed, “Five Days” asks you to absorb anguish, pain and serious ethical questions. It’s tough medicine, but it will do you good.

As Katrina drew near on Sunday, Aug. 28, 2005, Memorial and a separate long-term-treatment facility it housed called LifeCare held 1,800 to 2,000 people, including about 238 patients and 600 staff, plus family members, companions and neighborhood people who sought shelter in the hospital.

There were countless pets as well, and the area where many were kept behind the ICU was “filled with cages and the earsplitting barking and the stench of frightened animals.” Add in “the stench of sewage mixed with the odor of hundreds of unwashed bodies” as electric power dropped, tap water stopped and toilets backed up.

The medical staff focused on caring for and evacuating patients. The former grew increasingly difficult without power. Fink tells of a group of babies rescued in the first wave of helicopters, with one doctor throughout a flight operating an oxygen line by hand-pump for a 6-week-old born at 6 months.

Trucks, boats and helicopters slowly took away patients and relatives. Few of the staff departed. By Wednesday, the patient census had dropped to about 182. The feeling grew among a few of the medical staff that “not all of the patients would be getting out alive.”

Traditional triage was reversed. To “help speed the evacuation,” patients were assigned numbers 1, 2 and 3, from healthiest to most ill, with the No. 1 group getting out first.

Fink displays an uncanny knowledge of the actions of many people throughout the hospital. A six-page list of “Selected Individuals” that opens the book like a play’s dramatis personae includes more than 50 doctors, nurses, administrators and patients.

It was on Wednesday that a doctor, Ewing Cook, began euthanizing a few ailing and abandoned pets. Cook “prided himself as the go-to man for difficult end-of-life situations.” For an overweight comatose woman, he asked a nurse if she would mind “‘increasing the morphine and giving her enough until she goes.’”

The idea of euthanizing other patients was broached and rejected at various points. Eventually another doctor, Anna Pou, after consulting with Cook, would lead the effort to try to make some patients “comfortable” with morphine and other drugs.

Whatever the intent, more than a week after the hospital’s last living patients were evacuated on Thursday, rescue workers recovered 45 bodies, “the largest number of bodies found at any Katrina-struck hospital or nursing home.”

Fink is a trained physician who has worked in disaster relief and in conflict areas. Her restraint in the face of this charnel house is extraordinary.

Of course, careful language serves the demands of journalistic objectivity, not to mention legal constraints. It also ultimately makes it impossible to settle on a definitive perpetrator. Still, it’s clear that natural causes probably weren’t involved in some of those deaths.

The book’s second half, covering the investigation of Pou and two other staff members, presents more of Fink’s fine detective work, yet doesn’t ultimately offer the satisfaction of a clear villain. Many readers will find one or more anyway.

A thoughtful epilogue that ranges through several disasters since Katrina and assesses the lessons learned ends with a lousy report card. Fink points to misguided or inadequate disaster and emergency plans. It comes down unsurprisingly to the individuals making the decisions. It’s sad to realize that good decisions might not make such good books.